tach issues

SLACKER5.0

Founding Member
Mar 11, 2002
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great site guys.
i have a 1985 gt with a major tach problem it jumps all over the place. my original setup msd 6a and after market tach have worked great for the last 3 years untill lately, so i first changed to a autometer tach with the same result, so then i installed a 6al and tried both tachs and it still jumps all over.

so 2 tachs and 2 different msd boxes so whats next to check?

note i have changed every wire connection and location and have no change in my jumping tach. i did do a voltage check on my alt. last nite and it wold only put out 13.5 with no accessories and 12.5 with everything on.

could a weak alternator by chance cause these bad tach readings?

thanks bert
 
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